With the introduction of LTE network architecture in 3GPP Release 8 (Rel. 8) standards, a new type of UE temporary identifier is defined by the standards body and used by the Mobility Management Entity (MME) to address a user equipment (UE) when the UE registers with the Evolved Packet Core. This UE temporary identifier is called the Globally Unique Temporary Identifier (GUTI). Please see TS 23.003 for the definition of the GUTI. Due to the UE mobility between GPRS and LTE networks, and between UMTS and LTE networks, the UE temporary identifiers used in each of these different 3GPP access technologies need to be mapped between each other, i.e. from RAI+P-TMSI (Routing Area Identifier+Packet-Temporary Mobile Station Identifier) to GUTI or from GUTI to RAI+P-TMSI.
Yet, the requirement in 3GPP LTE Rel. 8 standards for mapping amongst disparate temporary identifiers (TIs) is a non-backward compatible requirement, which poses operational issues for network operators with significant network deployments that exploit radio technologies different from LTE. At least one issue arising from the requirement for mapping TIs associated with disparate radio technologies is that Location Area Codes (LACs) are restricted to a specific domain of values. However, network operators that exploit radio technologies such as 3GPP UMTS, 3GPP GPRS, or CDMA2000, are likely to have deployments that exceed such a restriction on LAC values. Thus, transition to 3GPP LTE radio technology is likely to result in substantial network re-planning in order to make the LAC assignments compliant with the current 3GPP LTE Rel. 8 standards protocol(s). Yet, the cost of such re-planning is prohibitively high and can impact adversely the service provided to current end-users during radio-technology transition periods.